1. Field of the Invention
The present invention relates to rocket engine combustion chamber fabrication and more particularly to the electrodeposition of metal alloys for the purposes of surface preparation.
2. Description of the Related Art
Large scale combustion chambers are often fabricated from alloys that are not conducive to the brazing operations required to build them. In situations such as this electrodeposited metal alloys are used to create a surface on which the brazing alloy will flow. The problem with electrodepositing alloy on large structures such as rocket engine combustion chambers is that a significant amount of current is required. The amount of current required is a function of the surface area in the plating solution. Currently one of two solutions to this problem exists. The first requires plating the part in sections and requires specialized cells to be fabricated and attached to the part. This is both labor intensive and time consuming. The second requires a large tank and current source to completely submerge and electroplate the part. A tank of this size requires specialized construction and results in a significant amount of plating solution waste. Special electrical wiring beyond that of standard high energy equipment is also required to supply the necessary amount of current.
U.S. Pat. No. 3,930,962, issued to G. M. Cook, et al, discloses a process and apparatus for producing thin copper foils by electroplating the copper onto a rotating drum serving as a cathode where the surface of the rotating drum is molybdenum or TZM alloy. The '962 patent does not address depositing coatings other than copper and also does not address deposits which require adherence to the cathode part.
U.S. Pat. No. 4,304,641, issued to J. Grandia, et al, discloses an apparatus and a method for rotary electroplating a thin metallic film. The apparatus includes a flow-through jet plate having nozzles of increasing size and uniformly spaced radially therethrough, or the same sized nozzles with varying radial spacing therethrough so as to provide a differential flow distribution of the plating solution that impinges on the wafer-cathode where the film is deposited. The spacing and size of the nozzles are critical to obtaining a uniform thickness. The electrical currents to the wafer and to the thieving ring are controlled by variable resistors so as to keep the electrical current to the cathode constant throughout the plating process. In a preferred embodiment the flow-through jet plate has an anode associated therewith in which the exposed area of the anode is maintained at a constant amount during the deposition. The method can simultaneously deposit with a uniform thickness and composition elements having a minimum gap or part size of 1 micrometer or less. U.S. Pat. No. 4,304,641 does not address the deposition of a metallic film on large parts with a conical geometry and is rather applied generally to the deposition on flat wafers with a desired film thickness on the order of micrometers.
U.S. Pat. No. 4,659,446 issued to D. A. Schafer, et al, discloses an apparatus for the electroplating printing cylinders or the like, cup-like shields of non-conductive acid-resistant material are secured at opposite ends of the cylinder for rotation with the cylinder, the shields extend radially outward and having a configuration such as to obtain a field distribution by which the metal deposited on the surface of the cylinder is of substantially uniform thickness and density throughout the length of the cylinder. U.S. Pat. No 4,659,446 does not address the electrodeposition of metal alloys on the typically conically shaped parts of rocket engine combustion chamber components as well as the deposition of metal alloys on the interior diameter of such components.